Laminated shingles are known in the art to be made from asphaltic roofing material overlaid upon one another, and secured together by means of an adhesive to provide a shingle having a thicker section. The anterior layer of the shingle has alternating tabs and cut out portions in the form of slots of various dimension in the lower end of the shingle, and an upper end of the shingle that is not divided into tabs. The posterior shingle layer, often called a backing sheet is applied, generally to the rear surface of the lower end of the anterior shingle layer, covering the rear surfaces of the tabs, such that the two shingle layers are not coextensive in area.
In applying the shingles to a roof, by means of fasteners such as nails, staples or the like in accordance with the teachings of the prior art, there is a longitudinal strip of double thickness through which the nails, staples or the like fasteners must be applied, in which they will pass through both shingle layers, such strip being above the area of the slots, but below the upper edge of the posterior shingle layer.
In order to most efficiently package a plurality of shingles in a given bundle, the posterior shingle layer is generally less than one half the width of the shingle, such that the shingles may be alternated in packaging without a stack of packaged shingles forming a “hump”. Typically, a backer strip or posterior shingle layer for a shingle of 12 inches in width, is usually 5⅞ to 5 15/16 inches wide in order to avoid the creation of an unduly high zone or “hump” in the middle of the shingle bundle, which is not desirable. Such 12 inch wide shingles then typically have an exposure width of 5 inches, leaving the common bond area between the laminated shingle layers to be a longitudinal strip of less than 1 inch in width.
Professional roofers find this width too narrow, as it interferes with efficient fastening of shingles to a roof, slowing down the speed of shingle application.
One approach to the problem is set forth in U.S. Pat. No. 6,145,265, granted Nov. 14, 2000, the complete disclosure of which is herein incorporated by reference. That approach has been to enlarge the width of the posterior shingle layer, to provide a larger (higher) common bond strip, of greater width than 1 inch, so that the nails, staples or like fasteners have a wider strip for passing through two layers.
Where laminated shingles have a common bond area that is too narrow, such as 1 inch or less, there can be a tendency for roofers to fail to apply the nail or staple fasteners into the common bond area, but to apply their fasteners above the common bond area, such that the fasteners pass through only the anterior shingle layer, and do not intercept the upper portion of the posterior shingle layer.
On roofs having a gentle slope or pitch, such misapplication of shingle fasteners may not be so susceptible to later problems. However, in roofs of steep pitch or slope, especially in warmer weather, such as summer weather, and in more southerly locations where roofs are subjected to more sun and greater heat in the summer, the temperature of a roof, particularly a dark roof, can reach 170° F. In more northerly locations in the summer, the temperature of a lighter colored roof, such as a white or light gray roof, in summer conditions may not reach a temperature higher than 140° F.
Most particularly, in more southern geographic areas, during the summer, and wherein roofs are of darker color, the temperature of the roof may approach the softening temperature of the normally bitumen-based adhesive, such as asphalt, which adheres two laminated layers of the laminated shingle together. With such softening of the bitumen-based adhesive, there leaves the possibility, especially for roofs of steeper pitch or slope, that the posterior shingle layer of any given shingle, if the fasteners have not penetrated such posterior layer when the shingle was applied to the roof, the posterior shingle layer, under its own weight, may overcome the adhesive quality and deformation resistance of the softening bitumen, and slide out beneath the anterior shingle layer, at least compromising the quality of the roof.